ML20149K396
| ML20149K396 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1983-057-00 | |
| Download: ML20149K396 (7) | |
Text
B.47-1 B.47 LER No. 373/83-057 Event
Description:
Scram, LOFW with RCIC Inoperable Date of Event: June 1, 1983 Plant: LaSalle I B.47.1 Summary Following a loss of feedwater and scram, the operators at LaSalle 1 had difficulty providing adequate makeup to the reactor vessel. As the reactor core isolation cooling (RCIC) system and the motor-driven feedpump were inoperable, operators blew down reactor pressure to 250 psig to allow makeup using the condensate pumps.
The status of the high pressure core spray (HPCS) system during the event is unclear. The conditional core damage probability estimated for this event is 2.1 x 10-5.
B.47.2 Event Description LaSalle 1 experienced trips of the condensate booster pumps and the reactor feed pumps around 0230 on June 1, 1983. Very shortly thereafter, the reactor scrammed on low level. Operators were apparently unable to restore the turbine-driven reactor feed pumps to service and the motor-driven pump was unavailable, as was the RCIC system. The status of the high-pressure core spray system during the event is not given.
Because of the difficulties experienced in providing adequate makeup to the vessel, operators blew down the vessel to 250 psig. This permitted them to make up with the condensate system.
Reactor pressure dropped from about 920 psig to about 250 psig in about one-half hour. Within a one-hour period, reactor vessel temperature dropped from 536'F to 418'F, thus exceeding Technical Specification cooldown limits. Subsequently, General Electric (GE) performed an assessment of design information provided by the reactor vessel supplier, Combustion Engineering. GE concluded that since the limiting components for thermal stress were the vessel flange bolts and, since the vessel water level never reached the flange, the vessel stresses experienced during the event were bounded by those experienced in normal shutdown. Stresses were apparently not calculated for other points in the vessel.
B.47.3 Additional Event-Related Information None.
B.47.4 Modeling Assumptions This event was modeled as a scram and loss of feedwater, with RCIC unavailable. HPCS was assumed to be available, although it is odd that it was not used during the event. (An additional calculation was performed assuming HPCS was unavailable, to explore the sensitivity of the model to this.)
LER No. 373/83-057
B.47-2 B.47.5 Analysis Results The conditional core damage probability estimated for this event is 2.1 x 105'. The dominant core damage sequence, highlighted on the event tree in Figure B.47.1, involves the observed scram, failure of the power conversion system, main feedwater failure, HPCS success and failure of residual heat removal (RHR). If HPCS is assumed to have been unavailable, the conditional core damage probability estimate is increased to 1.3 x 10-4.
LER No. 373/83-057
B.47-3 U) z
-- -- - - - -- U)
LU w U) cc U)
Cr z
0 0.
U) a-z CC 0
00.I Figure B.47.1 Dominant core damage sequence for LER 373/83-057 LER No. 373/83-057
B.47-4 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 373/83-057 Event
Description:
Scram. LOFW with RCIC inop Event Date: June 1. 1983 Plant: LaSalle I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OE+O0 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 2.1E-05 Total 2.1E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
103 trans -rx.shutdown PCS srv.ftc.<2 -MFW rhr.and.pcs.nrec CD 1.2E-05 5.5E-03 105 trans -rx.shutdown PCS srv.ftc.<2 MFW-hpci rhr.and.pcs.nrec CD 6.2E-06 2.8E-03 414 trans rx.shutdown rpt CD 6.7E-07 I.OE-OI 119 trans -rx.shutdown PCS srv.ftc.<2 MFW hpci RCIC srv.ads c CD 5.8E-07 8.1E-02 rd(inj) 413 trans rx.shutdown -rpt slcs CD 4.1E-07 i.0E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
103 trans -rx.shutdown PCS srv.ftc.<2 -MFW rhr.and.pcs.nrec CD 1.2E-05 5.5E-03 105 trans -rx.shutdown PCS srv.ftc.<2 MFW-hpci rhr.and.pcs.nrec CD 6.2E-06 2.8E-03 119 trans -rx.shutdown PCS srv.ftc.<2 MFW hpci RCIC srv.ads c CD 5.8E-07 8.1E-02 rd(inj) 413 trans rx.shutdown -rpt slcs CD 4.1E-07 i.0E-01 414 trans rx.shutdown rpt CD 6.7E-07 1.OE-01
- non-recovery credit for edited case SEQUENCE MODEL: d:\asp\models\bwrc8283.cmp BRANCH MODEL: d:\asp\models\lasallel.82 PROBABILITY FILE: d:\asp\models\bwr8283.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES LER No. 373/83-057
B.47-5 Branch System Non-Recov Opr Fail trans 1.5E-03 I.OE+00 loop 1.6E-05 5.3E-01 loca 3.3E-06 6.7E-01 rx.shutdown 3.5E -04 LGE-Ol PCs 1.7E-01 > 1.OE+00 1.OE+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 1.7E-01 > 1.OE+00 srv.ftc.<2 1.OE+00 1.QE+00 srv.ftc.2 1.3E-03 1.OE+00 srv.ftc.>2 2.2E-04 1.OE+00 MFW 2.9E-01 > 1.OE+00 3.4E -01 Branch Model: 1.OF.1 Train 1 Cond Prob: 2.9E-01 > 1.OE+00 hpci 2.OE-02 3.4E-01 RCIC 6.OE-02 > 1.OE+00 7.OE-01 > 1.OE+00 Branch Model: 1.OF.1 Train I Cond Prob: 6.OE-02 > 1.OE+00 srv.ads 3.7E-03 7.OE-01 1.OE-02 crd(inj) 1.OE-02 1.OE+00 1.OE-02 cond 1.OE+00 3.4E-01 1.OE-03 1pcs 2.OE-02 1.OE+00 Ipci 6.OE-04 1.OE'00 rhrsw(inj) 2.OE-02 1.OE+00 1.OE-02 rhr 1.OE-03 1.6E-02 1.OE-05 rhr.and.pcs.nrec 1.OE-03 8.3E-03 1.OE-05 rhr/-lpci 0.OE+00 1.0E+00 1.OE-05 rhr/lpci 1.OE+00 1.OE+00 1.OE-05 rhr(spcool) 2.OE-03 1.OE+00 1.OE-03 rhr(spcool)/-Ipci 1.OE-03 1.DE+00 1.OE-03 ep 2.9E-03 8.7E-01 ep.rec 1.7E-01 1.OE+00 rpt 1.9E-02 1.OE+00 slcs 2.OE-03 1.OE+00 1.OE-02 ads.inhibit 0.OE+00 1.OE+00 1.OE-02 man.depress 3.7E-03 1.OE+00 1.OE-02
- branch model file
- forced LER No. 373/83-057
B.47-6 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 373/83-057 Event
Description:
Scram. LOFW with RCIC inop Event Date: June 1. 1983 Plant: LaSalle 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.0E+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 1.3E-04 Total 1.3E-04 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
119 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI FRCIC srv.ads c CD 8.5E-05 2.4E-01 rd(inj) 138 trans -rx.shutdown PCS srv.ftc.2 HPCI srv.ads CD 1.6E-05 7.OE-01 103 trans -rx.shutdown PCS srv.ftc.<2 -MFW rhr.and *.pcs.nrec CD 1.2E-05 5.5E-03 109 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI FRCIC -srv.ads -c CD 5.7E-06 3.6E-03 ond rhr 111 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI FRCIC -srv.ads c CD 2.9E -06 1.8E-03 ond -lpcs rhr
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
103 trans -rx.shutdown PCS srv.ftc.<2 -MFW rhr.and.pcs.nrec CD 1.2E-05 5.5E-03 109 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI RCIC -srv.ads -c CD 5.7E-06 3.6E-03 ond rhr 111 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI RCIC -srv.ads c CD 2.9E-06 1.BE-03 ond -lpcs rhr 119 trans -rx.shutdown PCS srv.ftc.<2 MFW HPCI RCIC srv.ads c CD 8.5E-05 2.4E-01 rd(inj) 138 trans -rx.shutdown PCS srv.ftc.2 HPCI srv.ads CD 1.6E-05 7.OE-01
- non-recovery credit for edited case SEQUENCE MODEL: d:\asp\models\bwrc8283.cmp BRANCH MODEL: d:\asp\models\lasallel.82 LER No. 373/83-057
B.47-7 PROBABILITY FILE: d:\asp\models\bwr8283.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 1.5E-03 1.OE+00 loop 1.6E-05 5.3E-01 loca M.E-06 6.7E-01 rx. shutdown 3.5E-04 1.OE-01 PCS 1.7E-01 > 1.OE+OO 1.OE+0O Branch Model: I.OF.1 Train 1 Cond Prob: 1.7E-01 >1.OE+0O srv.ftc.<2 1.OE+0O 1.OE+0O srv.ftc,2 1.3E-03 1.OE+OO srv.ftc,>2 2.2E-04 1.OE+OO MFW 2.9E-01 > 1.OE+OO 3.4E-O01 Branch Model: 1.OF.1 Train 1 Cond Prob: 2.9E-01 > 1.OE+OO HPCI 2.OE-02 > 1.OE+OO 3.4E-O1 > 1.OE+OO Branch Model: 1.OF.1 Train 1 Cond Prob: 2.OE-02 >1.OE+OO RCIC 6.OE-02 > 1.OE+OO 7.OE-01 > 1.OE+OO Branch Model: 1.OF.1 Train I Cond Prob: 6.OE-02 > 1.OE+OO srv.ads 3.7E-03 7.OE-O1 1.OE-02 crd(inj) 1.OE-02 1.OE+OO 1.OE-02 cond 1.OE+0O 3.4E-01 1.OE-03 Ipcs 2.OE-02 1.OE+OO Ipci 6.OE-04 1.OE+OO rhrsw(inj) 2.OE-02 1.OE+00 1.OE-02 rhr 1,OE-03 1.6E-02 1.OE-05 rhr.and.pcs.nrec 1.OE-03 8.3E-03 1.OE-05 rhr/-lpci O,OE+OO 1.OE+OO 1.OE-05 rhr/lpci 1.OE+00 1.OE+00 1.OE-05 rhr(spcool) 2.OE-03 1.0 +00 1.0E-03 rhr(spcool )/-Ipci 1.OE-03 1.OE+00 1.OE-03 ep 2.9E-03 8.7E-01 ep.rec 1.7E-01 1.OE+00 rpt 1.9E-02 1.0 +00 slcs 2.OE-03 1.OE+00 1.OE-02 ads.inhibit O.OE+OO 1.OE+00 1.OE-02 man.depress 3.7E-03 1.OE+00 1.OE-02
- branch model file
- forced LER No. 373/83-057